SIMBAD references

We show that the candidate progenitor of the core-collapse SN 2011dh in M 51 (8 Mpc away) was fading by 0.039±0.006 mag/yr during the 3 years prior to the supernova, and that this level of variability is moderately unusual for other similar stars in M 51. While there are uncertainties about whether the true progenitor was a blue companion to this candidate, the result illustrates that there are no technical challenges to obtaining fairly high precision light curves of supernova-progenitor systems using ground-based observations of nearby (<10 Mpc) galaxies with wide-field cameras on 8 m class telescopes. While other sources of variability may dominate, it is even possible to reach into the range of evolution rates required by the quasi-static evolution of the stellar envelope. For M 81, where we have many more epochs and a slightly longer time baseline, our formal 3σ sensitivity to slow changes is presently 3 mmag/yr for an M_V≃ -8 mag star. In short, there is no observational barrier to determining whether the variability properties of stars in their last phases of evolution (post-carbon ignition) are different from earlier phases.